Summary of similarities and differences between onbeforeunload and onunload events

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Summary of similarities and differences between onbeforeunload and onunload events_javascript skills

May 16, 2016 pm 05:31 PM

onbeforeunload

1) Similarities and differences
Same points: onunload and onbeforeunload are called when refreshing or closing. They can be specified through window.onunload in the <script> script or specified in <body>. Differences: a) onbeforeunload is executed before onunload, and it can also prevent the execution of onunload. b) onbeforeunload is called when going to the server to read a new page, but has not yet started reading; nunload has read the new page that needs to be loaded from the server, and is called when the current page is about to be replaced. c) onbeforeunload can prevent the page from being updated and closed. But onunload cannot. The execution sequence of onload, onbeforeunload, and onunload events: When opening the page: only execute onload When closing the page: first onbeforeunload, then onunload When refreshing the page: first onbeforeunload, then onunload, then onload 2) onbeforeunload, onunload events Triggered when: a) Close the browser window b) When going to other pages through the address bar or favorites c) When clicking return, forward, refresh, or one of the homepages d) When clicking a URL link to other pages e) When calling any of the following events: click, document write, document open, document close, window close, window navigate, window NavigateAndFind, location replace, location reload, form submit. f) When using window open to open a page, pass the name of the window on this page to the page to be opened. time. g) When reassigning the value of location.href. h) When submitting a form with a specified action through the input type="submit" button. can be used in the following elements: BODY, FRAMESET, window Browser support: IE4 /Win, Mozilla 1.7a, Netscape 7.2, Firefox0.9 3) Solve the problem of not calling onbeforeunload when refreshing the page 4) onbeforeunload prevents the update and closing of the page onbeforeunload="return 'Do you want to leave this page now';"></script>

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